1. Field of the Invention
The present invention relates to the field of antenna control system testing and, more particularly, to systems in which a simulated target or simulated antenna pattern is employed to test the responses of an antenna control unit.
2. Description of the Prior Art
As computers play a more influential role in the control of tracking telemetry antenna systems, the capabilities of these antenna systems becomes more sophisticated. Testing and characterizing these features is very difficult since a cooperative target carrying sophisticated electronics is required to set up the special conditions that these advanced capabilities are meant to handle. At present, there is no known way to fully and reliably test these tracking control features without the use of expensive, fast maneuvering airborne or seaborne test platforms.
Prior to the present invention, antenna control systems required field tests including the use of transmitters, antennas, and receivers. Radio frequency (RF) signals would be generated by the target's transmitter and then transmitted to the antenna. The receiver would then process the signal and communicate all relevant information to an antenna control unit (ACU). Once provided with the necessary information, the antenna control unit would generate the proper control functions to continue tracking the target. This process was burdensome and required considerable expense. These tests were even more burdensome and expensive when using multiple targets.
Moreover, the antenna control system could not be readily tested for identical target telemetries under differing weather conditions or varied signal effects (e.g., fading or multi-path) because the target's path could not easily be duplicated. Multi-path is caused by reflections of target echoes from other objects or surfaces causing echo energy to arrive at the antenna by other than the direct return path. Fading occurs when the signal attenuates to a point where it is difficult to detect for a variety of reasons.
The broad concept of a simulator used for testing is disclosed in U.S. Pat. No. 4,969,819 to James. The '819 patent is directed to an electronic counter measures simulator for radar system vulnerability studies. The simulator disclosed in the '819 patent employs RF signal generators to create simulated target return signals which include the effects of propagation factors as well as electronic counter measure simulation. The RF signal is then transmitted to the radar system under test and the signal is subsequently processed.
The '819 patent is directed solely to the testing of radar systems and does not overcome many of the disadvantages earlier described.
Another simulation system is disclosed in U.S. Pat. No. 3,982,244 to Ward et al. The '244 patent is also directed to the testing of radar systems and discloses the use of multiple simulators to generate an intermediate frequency signal containing target data. These signals provide data to the radar system which is representative of known target return signals, clutter, electronic counter measure, and other pertinent noise signals. This data is then processed and radar system control functions are produced.
The '244 patent is also directed solely to the testing of radar systems and does not overcome the problems associated with testing complex and sophisticated telemetry antenna control systems.